Thanks guys. So, if I pick up a barrel with the extension already installed, it would be unlikely that there would be an issue, correct? I don't plan to buy a cheap barrel and the upper is said to be mil spec, plus a FZ BCG should be trust worthy. My alternative is to have my wife's cousing fire it for the first time while I take cover.... I mean, go purchase refreshments... For him and whomever he happens to bring with him. Once I can find a barrel and accessories, I'll be back to quiz you guys on the gas system and potential concerns there.